Chylous effusions
Chylous effusions or chylothorax occurs when there is lymphatic chyle in
the chest cavity and/or pleural space as a result of intrinsic
abnormalities of the lymphatic system or secondary to thoracic duct
injury (trauma, surgery, malignancy, cardiovascular disease). Primary
disorders of pulmonary and pleural lymphatic flow predispose to impaired
lymphatic drainage, increased trans-pleural filtration pressure
(lymphatic hypertension), retrograde lymphatic flow and increased
permeability that results in chylous effusion or chylothorax(Figure 1b) . These disorders are sometimes referred to as
pulmonary Lymphatic Perfusion Syndromes (PLPS). Chylous effusions
typically present with respiratory symptoms such as dyspnea, chest pain,
cough, and fatigue.
Abnormal development of the native lymphatic system presents as
lymphangiomatosis or lymphangiectasia. Lymphangiomatosis is a
generalized term for the over-proliferation of malformed and poorly
functional lymphatics in the lungs (Figure 1b) . Abnormal
lymphatics can infiltrate a single organ or present as multifocal
disease with infiltrations into bone and surrounding tissue. Pulmonary
lymphangiomatosis can present with non-specific respiratory symptoms of
progressive cough, wheezing, or dyspnea. Congenital pulmonary
lymphangiectasia is characterized by dilated lymphatics in the
subpleural and interlobular lymphatic vessels that fail to drain
appropriately. Primary pulmonary lymphangiectasia is hypothesized as a
failure of the normal large lymphatic channels to regress mid-lung
development (at ~20 weeks). Lymphangiectasia commonly
presents with non-specific respiratory distress.
Chyle aspirated via thoracentesis is milky in appearance with lymphocyte
predominance and biochemical analysis often with a triglyceride
concentration >110 mg/dL. In the unfed state, chylous fluid
can be clear yellow in the absence of chylomicrons.